1. Field of the Invention
The present invention relates to gas turbine engines, and more particularly herein to jet engines especially adapted for travel at high supersonic and hypersonic velocities.
2. Description of the Prior Art
In conventional jet engines, where there is a forward compressor, a rearwardly positioned turbine, and an intermediate combustion chamber, the compressor is exposed to the "total temperature" generated by the flight speed of the aircraft. As the flight speed is increased the power requirements of the jet engine progressively increase while concurrently higher temperatures are generated at the compressor inlet. To compensate for such increased temperatures, it becomes necessary to increase the temperature at the turbine inlet by increasing the fuel/air ratio mixture of the gases entering the combustion chamber ahead of the turbine, in order that the increase in power output available for propulsion is to be obtained. However, as the turbine temperatures approach the limit of turbine blade material capability, increased complexity of the turbine blading and engine design is required, such as blade cooling to permit the metal temperature capabilities to be extended into the higher speed regimes. Finally, a limiting turbine temperature is reached even with blade cooling, and attempts to design an engine which is capable of yet further velocity increases results in severe performance degradation of the engine. Thus, within the practical limitation of present technology, the upper economical limit of speed for jet engines of this conventional design is moderately in excess of Mach 3.
U.S. Pat. No. 3,158,990, Ferri, illustrates a ram jet engine intended for travel at higher than usual velocities. In this engine, there is a forwardly positioned turbine at the engine inlet which extracts energy from the ram air passing into the inlet, so that the temperature of the air passing out the rear end of the turbine is at a reduced temperature. This air then passes through a heat exchanger operating at a sufficiently high temperature to add energy to the air that has passed through the turbine. This air then passes through a compressor and thence out the exhaust nozzle of the engine.
A number of other patents show other engine component arrangements. For example, U.S. Pat. No. 2,623,356, Coanda, shows a turbo jet engine which directs its exhaust gases through a compressor to increase the intake-discharge pressure differential of the engine. This compressor is driven by a forwardly extending longitudinal shaft connected to an upstream turbine.
U.S. Pat. No. 3,098,632, Christenson, shows an apparatus which is mounted to an aircraft to function as a fuel tank and also as a jet engine. The principle of operation of the engine components is generally conventional.
U.S. Pat. No. 3,105,661, Ferri, shows a jet engine where there is a compressor positioned at a radially inward position and a turbine connected to the compressor at a radially outward location. The air passing through the radially outward turbine has energy extracted therefrom and therefore experiences a temperature reduction. This air is directed around the skin of the engine for cooling the engine at high speeds.
U.S. Pat. No. 3,382,678, Reh, shows an engine particularly adapted for generating a high pressure efflux for a boat. Air from a compressor is directed to a combustion chamber. The hot exhaust from the combustion chamber is split to drive a turbine and also to drive a second stage compressor, whose discharge is compressed gas that is used as the exhaust gas for propulsion.
U.S. Pat. No. 3,241,310, Hoadley, shows a jet engine where a cryogenic fuel is placed in heat exchange relationship with the gases in the combustion chamber of the engine. The vaporized cryogenic fuel is then directed through the interior of the rotor blades of a compressor and discharged from the trailing edge of the blades to supply added power to the blades.
U.S. Pat. No. 3,369,361, Craig, shows a gas turbine power plane which utilizes a water spray at the turbine discharge to reduce pressure of the exhaust gases passing through the turbine.